/*
 * Copyright 2009 Jiwei Xu (http://www.xujiwei.com)
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
 
provide("Undo.UndoManager");

UndoManager = Class({
    Initialize : function() {
        this.undo = [];
        this.redo = [];
        this.CanUndo = false;
        this.CanRedo = false;
    },

    Push : function(cmd) {
        this.undo.push(cmd);
        this.redo.splice(0, this.redo.length);
    },

    Undo : function(count) {
        count = count || 1;
        var undoList = this.undo, redoList = this.redo;
        while (count-- && undoList.length > 0) {
            var cmd = undoList.pop();
            cmd.Undo();
            redoList.unshift(cmd);
        }
        this.CanUndo = undoList.length > 0;
        this.CanRedo = redoList.length > 0;
    },

    Redo : function(count) {
        count = count || 1;
        var undoList = this.undo, redoList = this.redo;
        while (count-- && redoList.length > 0) {
            var cmd = redoList.shift();
            cmd.Redo();
            undoList.push(cmd);
        }
        this.CanUndo = undoList.length > 0;
        this.CanRedo = redoList.length > 0;
    }
});